Electronics > Beginners

W27C512 EEPROM Frustrations

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wraper:

Bud:
There is your problem. Buy from a reputable source.

Ian.M:
Implement ID readout with A9 pulsed to 12V (see Table of Operating Modes' on page 7 and left side of 'Erase Waveform' diagram on page 13).  That should be non-destructive on any JEDEC compatible EPROM or EEPROM >64K.   

Before attempting to program a 'new' chip, check the device ID.  If you don't get the correct ID bytes, DA 08, its a remarked fake, not a genuine Winbond W27C512.  If it lets the holy smoke out, then its probably not even a non-volatile memory chip!  If it already has data in it, its recycled not new.

CRCLARKE:

Upon closer inspection of the chips, maybe? probably? the have been rebranded. There are some definite physical variations in the chips, but even the working ones have some variances.

but knowing this information doesn't help a lot....

so i guess the lesson is:


--- Quote from: Bud on January 05, 2020, 06:30:27 pm ---There is your problem. Buy from a reputable source.

--- End quote ---


but none of shady sellers admit to being "non-reputable"

Where do you get Your eeproms from?


--- Quote from: Ian.M on January 05, 2020, 06:42:56 pm ---Implement ID readout with A9 pulsed to 12V (see Table of Operating Modes' on page 7 and left side of 'Erase Waveform' diagram on page 13).  That should be non-destructive on any JEDEC compatible EPROM or EEPROM >64K.   

Before attempting to program a 'new' chip, check the device ID.  If you don't get the correct ID bytes, DA 08, its a remarked fake, not a genuine Winbond W27C512.  If it lets the holy smoke out, then its probably not even a non-volatile memory chip!  If it already has data in it, its recycled not new.

--- End quote ---

Hey, that's a good idea!!!

also, less than half of the chips were erased when i received them

wraper:
Clearly counterfeit. Packages are different but marking is exactly the same. Genuine components from different batches cannot have exactly the same lot, date code and other information (bottom row). Some ICs are obviously salvaged since there are soldering signs on their leads. Certainly try rubbing them with acetone, some look like they could be sanded and blacktopped.

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